1. Field of Invention
The present invention relates to compressing data. More specifically, the present invention relates to methods and apparatus for efficiently and effectively compressing signals for transmission on a network such as a cell based or packet based network.
2. Description of the Related Art
Conventional techniques for compressing delay sensitive signals such as telephony or audio signals are limited. Any audio, video, or data sequence specified for transmission with minimal delay is referred to herein as a delay sensitive signal. Examples of delay sensitive signals are real-time video streams and telephony signals. In typical implementations, a delay sensitive signal such as a telephony signal is companded for transmission on a telephony network. A signal that represents an input analog signal is compressed into logarithmic segments, where each logarithmic segment is quantized and coded using uniform quantization. Such a signal is referred to herein as a companded signal. To improve bandwidth efficiency for packet or cell-based transport of normal telephony audio signals, the telephony signals are then often further compressed by the interworking hardware between Public Switched Telephone Networks (PSTN) or General Switched Telephone Networks (GSTN) and transport IP networks.
However, the conventional techniques for compression are typically inadequate, lossy, or inefficient. Consequently, it is desirable to provide improved techniques for compressing data, particularly delay sensitive data, for transmission over a network such as a packet or cell based network.